1. Field of the Invention
The present invention is directed to the field of automotive lamp and socket assemblies and more specifically to the area of an improved retaining mechanism used in conjunction with an improved lamp base to secure a lamp within a socket.
2. Description of the Prior Art
Prior art wedge base lamp bulbs and sockets are disclosed in several patents. For instance, U.S. Pat. No. 4,114,972 discloses a socket which is used to support and retain a single filament wedge base bulb. The socket is shown as employing asymmetrical flexible ribs formed with partially cylindrical surfaces to mate and resiliently grip vertical ribs on the sealed base of the bulb envelope. The asymmetry of the gripping ribs causes the inserted base of the bulb to be slightly rotated in a counterclockwise direction in order to force the exposed filament wire leads into electrical contact with the socket contact elements.
U.S. Pat. No. 3,676,834 discloses a structure for mounting and electrically connecting a wedge base type lamp bulb in a resilient socket, wherein the bulb is gripped above its base on the envelope portion.
U S. Pat. No. 3,950,061 also discloses a socket for a wedge base lamp bulb. In that patent, the socket contains a recessed seat in which the enlarged cylindrical envelope of the bulb is engaged. The seat limits the downward movement of the lamp bulb in the socket, while a pair of opposed flexible resilient ribs within the recessed seat of the socket compressibly engage the envelope and hold the lamp in place.
In several of the prior art structures, there is a lack of positive retention. As such, severe vibration or thermal cycling may cause the lamps to come loose from the sockets. Therefore, in automotive external lighting applications, prior art wedge base lamps have not been deemed to be suitable alternatives to conventional bayonet lamp bulbs.
A conventional bayonet lamp bulb is usually formed as a glass envelope cemented into a cylindrical metal lamp base with its ground filament leads commonly soldered to the base and its other filament leads soldered to individual terminals at the insulated bottom of the base. Bayonet lamp sockets are such that the lamp bulbs must be properly aligned, inserted and rotated against an outwardly biased set of contact terminals. However, corrosion of the biasing springs and terminals often causes the removal of the lamp bulbs to be difficult. In addition, the construction of such lamp bulbs requires more steps to fabricate then the wedge type bulbs, that have been found to be desirable substitutes in other applications.